1. Field of the Invention
The present invention relates to a vehicle collision preventing apparatus in which an obstacle is detected in a traveling direction of the vehicle and a judgment is made as to whether or not an own vehicle collides against the obstacle.
2. Prior Art
Recently, various approaches for safe driving have been attempted. One of these approaches is the development of an ASV (Advanced Safety Vehicle). The ASV includes techniques such as issuing alarm to a vehicle driver, stopping a vehicle by braking automatically, changing vehicle speeds automatically so as to maintain a proper inter-vehicle distance and the like by detecting obstacles ahead of the vehicle with TV cameras or laser beam-radar apparatus and the like and judging a possibility of collision with the obstacles.
As an example of this kind of technology, Journal of The Society of Automotive Engineers of Japan Vol. 43, No. 2, 1989, an article "Rear-end Collision Warning System using Laser for Heavy-duty Trucks" discloses a technology in which a vehicle speed of the preceding vehicle and a relative vehicle speed of the subject vehicle with respect to the preceding vehicle are calculated based on a vehicle speed of the subject vehicle and a distance between the subject vehicle and the preceding vehicle detected by a laser beam radar, and when the distance between two vehicles comes within a safe inter-vehicle distance calculated based on this relative vehicle speed, an alarm is sent out to warn a possible collision against the preceding vehicle.
However, this warning system is still insufficient because hazard is judged by observing only the preceding vehicle or only an obstacle ahead of the subject vehicle without taking other situations ahead of the preceding vehicle into consideration.
Assuming such a situation that the preceding vehicle comes to a sudden stop to avoid a collision with an obstacle, it is necessary to raise an alarm with a sufficient time margin. This requires to establish a very large inter-vehicle distance which may allow other vehicles to cut in between the subject vehicle and the preceding vehicle.
Further, since such a safe driving technique as noticing only the behavior of the preceding vehicle is fundamentally based on an assumption that the driver of the preceding vehicle always takes a reasonable behavior, it is impossible to expect a further safe driving.